- The target Raw of each patient should be determined within 72 hours after their admission to intensive care unit. After confirming no inhaled bronchodilator given in preceding 2 hours (for fenoterol) or 12 hours (for salmeterol/fluticasone), we will deliver 3 consecutive doses of 4 puffs, 8 puffs and 16 puffs of fenoterol MDI (100 mcg/puff, Berotec;Boehringer Ingelheim, Ingelheim, Germany) inhalation with each dose 15 minutes apart. The Raw measured 15 minutes later is assigned as this patient's personal target Raw.